<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
  <input type="text">
  <p></p>
</body>
<script>
  const input = document.querySelector('input');
  const p = document.querySelector('p');
  const data = {
    str:'大连'
  };
  let $data = {str:data.str};
  Object.defineProperty(data,'str',{
    get(){
      return $data.str;
    },
    set(v){
      $data.str = input.value = p.innerText = v;
    }
  });
  input.value = p.innerText = data.str;
  input.oninput = function (){
    data.str = this.value;
  };

</script>
</html>